1. Field of the Invention
The present invention relates to an electronic ring sounder for a speaker telephone, which functions in place of the conventional bell in a handset telephone instrument when the speaker telephone is used independently of such an instrument.
2. Description of the Prior Art
Telephone amplifiers have gained considerable acceptance as an add-on for converting an existing handset telephone instrument to a speaker telephone. Typically the telephine amplifier is connected in parallel with the handset instrument, so that when a call is received, the ring signal from the telehone line causes the bell in the handset instrument to ring. The user then has the option of either lifting the handset or switching in the telephone amplifier while leaving the handset physically on the cradle.
In the telephone amplifier, incoming speech is amplified and reproduced by a loudspeaker. The user's voice is picked up by a microphone and amplified for transmission to the line. Appropriate voice responsive circuitry isolates the outgoing and incoming signals, and prevents audio feedback from the loudspeaker to the microphone. The telephone amplifier offers the convenience of "no hands" operation.
For outgoing calls, the dial or tone-enabling pushbuttons on the handset telephone instrument are used to dial a number. Thus with an add-on telephone amplifier, the existing handset telephone instrument provides both the bell which rings to indicate an incoming call, and the dial or pushbutton mechanism for initiating an outgoing call.
By providing a telephone amplifier with dialing and ring sounding capabilities, the unit can act as a self-contained speaker telephone. It can be used completely independently of a handset telephone instrument. Dialing mechanisms for use with such a speaker telephone are known per se. The principal object of the present invention is to provide an electronic bell or ring sounder for such a speaker telephone which functions in place of the conventional telephone bell.